I have an 87 t/a orginal LB9 car, 2.73 posi, i just put a 71 400 4-bolt punched and stroked to a 434 in it. It has Edelbrock Performer Rpm Heads ported and polished w/steam holes drilled, the bottom end of the motor is all forged w/moly rings, comp 1.52 roller rockers, had the stock tpi intake ported and polished. my ? is should i have the plenum and runners replaced or ported out also? the entire ignition is MSD w/6AL I have 2 Stages of NOS for the engine but i am not entirely sure what all needs 2 be done to make the TPI work right for this engine considering that it was made for the LB9 305, I have a hypertec chip but i've been told that its also obsolete since i now have a 434 any ideas or comments would be appricated. I have the engine in the car but i've yet to complete it. Has anyone tried running a tpi on a 434??

 

Tons of torque and some broken drive train parts.

 

You'll need a custom tune for that thing. That Hypertech chip isn't all that to begin with. They are OK on stock engines but that's about it. The stock TPI setup is insufficient for what you've got going on there. TPI runs out of breath at 4500rpm on LB9 and L98 engines. For your setup you should probably step up to a Holley Stealth Ram or a TPIS Mini-Ram. They'll serve you far better than any ported TPI system.

 

if you insist on keeping tpi you'll need to hog out the plenum and get better runners and a new intake base custom tune and i'd guess 36# injectors. you'll still be running out of air though. unless you have a good reason to stick with tpi you'd need a stealth or mini ram like mentioned above and probably need that ported to hell.

 

You can get it in the ball-park by installing 30 lb/hr fuel injectors. Then once running, take it to an experienced tuner ASAP.
I would suggest running the ECM in OLSD mode (tuner will know what this is).

As for power, you're going to need a major exhaust system upgrade. 1.75" primary long-tube headers with dual 3" exhaust would be a good place to start. I think Mufflex makes a coupler so that you can run a single 4" if you want.

When you get to the point of using the N2O, expect more power gain than what your jetting projects. At WOT with this engine, the N2O will be delivered into a lower pressure environment than usual due to the vacuum you will develop in your TPI intake manifold. This will boost the power gain in two ways - the nozzle flow will increase, and you will get a greater increase in intake charge density due to the relatively higher % of N2O to ambient air that the engine is ingesting. The ramming effect of the long TPI runners will also add to an extremely large torque peak that will make traction difficult. Even with a 27 or 28 inch tire you'll probaby have to soften up the lower RPM range by taking some spark timing away.

Find a very experienced tuner that can handle all of this, because it has to be done on the EPROM.

 

I've done stock TPI on a mild 383 and can tell you what to expect...TORQUE! My 1991Vette 'vert may not have been fast with the TPI383/700R4 combo, but it sure was a giggle-inducing power-slide/drift machine. Save money for tires...

 

Your joking right?